| 摘要 |
A method and apparatus for performing adaptive differential pulse code modulation. The method and apparatus is particularly adapted for compliance with the ITU-T G.726 international standard. Certain intermediate values, including Y and SE, needed to compress or decompress a given sample are pre-calculated prior to receipt of the actual sample to which they correspond. Accordingly, when the sample is received, intermediate variables Y and SE are essentially immediately available. This allows the output value SR (during a decompression cycle) or I (during a compression cycle) to be available one clock cycle after receipt of a sample. The remaining clock cycles corresponding to that sample period are used to precalculate the intermediate variables Y and SE for the next sample. The method and apparatus requires only fifteen clock cycles per conversion.
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